1. Field of the Invention
The present invention relates to a magnetic tape cartridge, and more particularly to a magnetic tape cartridge where a single reel with magnetic tape wound on the outer periphery of a reel drum is rotatably housed within a cartridge case.
2. Description of the Related Art
In magnetic tape cartridges, which are being used as storage media that are employed in external storage units for computers, etc., there is known a type where a single reel with magnetic tape wound thereon is rotatably housed within a cartridge case.
This type of magnetic tape cartridge has only a single reel within the cartridge case. Because of this, when the magnetic tape is loosened by shock due to the cartridge falliing, etc., the loose part cannot be absorbed and therefore there is a disadvantage that the magnetic tape will be damaged.
Hence, a magnetic tape cartridge equipped with a reel locking mechanism which restrains rotation of the reel during periods of non-use has been provided. The reel locking mechanism is disclosed, for example, in Japanese Unexamined Patent Publication No. 11 (1999)-238352. The reel locking mechanism is equipped with a locking member movable toward and away from the reel to restrain rotation of the reel, an urging member (e.g., a coil spring) for urging the locking member in a locking direction, and an unlocking member which rotates integrally with the reel to move the locking member in an unlocking direction in accordance with the chucking operation of the rotation-drive means of a cartridge drive unit.
The locking member is equipped with a locking tooth portion, which meshes with a locking tooth portion formed in the reel to forcibly lock rotation of the reel during non-use. That is, the locking member is constructed so that the magnetic tape is not tightened or loosened by shock due to the cartridge falling, etc.
The bottom surface of the cartridge case has a circular opening, which is exposed to the outside so that the bottom surface of the reel drum can be chucked by the rotation-drive means of the cartridge drive unit. The circumference of the opening is formed into a receiving surface that receives the reel during non-use. During non-use, the urging force of the urging member for urging the locking member in a locking direction is exerted on the reel through the unlocking member, whereby the reel is pressed against the receiving surface of the cartridge case.
This type of magnetic tape cartridge, incidentally, is often loaded into the cartridge drive unit in a posture where the axis of the reel drum becomes vertical. However, in the case of an automatic loader being equipped with a great number of cartridges, for example, each cartridge is loaded into the cartridge drive unit in a state where the axis of the reel drum is horizontal. That is, the cartridges are vertically placed.
In that case, since there is a radial clearance of some magnitude between the cartridge case and the reel, the vertically placed reel will be moved downward by the amount of the radial clearance, notwithstanding the fact that the reel is pressed against the receiving surface of the cartridge case by the urging force of the urging member.
On the other hand, the cartridge case is positioned by the positing means of the cartridge drive unit, and the rotation-drive member of the cartridge drive unit performs a chucking operation with the position of the cartridge case as its reference. Because of this, if the reel is moved downward when it is vertically placed, the center axis of the reel drum will be shifted from that of the rotation-drive member of the cartridge drive unit. Consequently, there is a problem that chucking failure of the rotation-drive member with respect to the reel drum will occur.
The present invention has been made in view of the aforementioned circumstances. Accordingly, it is the primary object of the present invention to provide a magnetic tape cartridge which is capable of preventing chucking failure when it is vertically loaded into a cartridge drive unit.
To achieve this end and in accordance with the present invention, there is provided a first magnetic tape cartridge comprising:
a cartridge case in which a single reel with magnetic tape wound on an outer periphery of a reel drum is rotatably housed; and
a locking member, provided within the reel drum so that it is movable between a locking position and an unlocking position in an axial direction of the reel, for locking the reel to restrain rotation of the reel during non-use;
wherein a first radial clearance between the locking member and the reel drum is set smaller than a second radial clearance between the reel and the cartridge case.
In the case where the reel drum has reinforcement ribs on the inner peripheral surface thereof, the aforementioned first radial clearance is the clearance between the outer peripheral surface of the locking member and the outer ends of the ribs. In the case where the cartridge case is equipped with a circular arc rib along the outer periphery of the reel, the aforementioned second radial clearance is the clearance between the outer periphery of the reel and the inner peripheral surface of the circular arc rib.
According to the first magnetic tape cartridge of the present invention, the first radial clearance between the locking member and the reel drum is made narrower than the second radial clearance between the reel and the cartridge case. Therefore, even if the reel is caused to move downward by the weight of magnetic tape when the magnetic tape cartridge is vertically loaded into the cartridge drive unit, the inside of the reel drum immediately abuts the outer periphery of the locking member and regulates downward movement of the reel. As a result, the amount of the core axis misalignment of the reel drum with respect to the rotation-drive member of the cartridge drive unit is held down to a slight value. Thus, chucking failure due to core axis misalignment is prevented.
In accordance with the present invention, there is provided a second magnetic tape cartridge comprising:
a cartridge case in which a single reel with magnetic tape wound on an outer periphery of a reel drum is rotatably housed;
a circular opening formed in a bottom surface of the cartridge case so that a bottom surface of the reel drum can be chucked by rotation-drive means of a cartridge drive unit; and
a receiving surface, formed in the circumference of the opening, against which the reel is pressed in an axial direction of the reel with urging means during non-use;
wherein the receiving surface is enlarged in a radial direction of the reel.
In the second magnetic tape cartridge, a layer of material having great contacting and sliding resistances, such as a rubber type material, may be provided on the receiving surface by attachment of a sheet or a dichroic injection molding method.
According to the second magnetic tape cartridge of the present invention, the sliding resistance between the receiving surface and the reel is increased by enlargement of the receiving surface. Therefore, even when the magnetic tape cartridge is vertically loaded into a cartridge drive unit, the reel can be prevented from being moved by the weight of magnetic tape and it becomes possible to prevent chucking failure due to core axis misalignment.
In addition, since enlargement of the receiving surface enhances the performance of maintaining the posture of the reel even when it is horizontally placed (the reel is less likely to be tilted), the degree of parallelization with respect to the rotation-drive member of the cartridge drive unit is enhanced, and consequently, chucking failure can be prevented.
Furthermore, the effect of preventing core axis misalignment in the vertically placed state can be further enhanced by providing the rubber layer, which has great contacting and sliding resistances, on the receiving surface, or by enlarging the receiving surface and also increasing the urging force of the urging member.
In accordance with the present invention, there is provided a third magnetic tape cartridge comprising:
a cartridge case in which a single reel with magnetic tape wound on an outer periphery of a reel drum is rotatably housed;
a circular opening formed in a bottom surface of the cartridge case so that a bottom surface of the reel drum can be chucked by rotation-drive means of a cartridge drive unit;
a receiving surface, formed in the circumference of the opening, against which the reel is pressed in an axial direction of the reel with urging means during non-use; and
a regulation means, provided between the receiving surface and a reel surface that is pushed against the receiving surface, that engages in a convex-concave manner for regulating radial movement of the reel during non-use.
In the third magnetic tape cartridge, the aforementioned regulation means is constructed of an annular groove formed concentrically in the receiving surface of the cartridge case, and an annular ridge formed in the reel surface so that it can be fitted in the annular groove. The regulation means may also be constructed of a first inclined surface continuous to the receiving surface of the cartridge case, and a second inclined surface formed in the reel so as to be opposed to the first inclined surface.
According to the third magnetic tape cartridge of the present invention, a regulation means for regulating radial movement of the reel during non-use is provided between the receiving surface of the cartridge case and a reel surface that is pushed against the receiving surface. Therefore, even in the case where the magnetic tape cartridge is vertically loaded into the cartridge drive unit, the radial movement of the reel by the weight of magnetic tape is regulated by the regulation means and therefore the amount of the core axis misalignment with respect to the rotation-drive member of the cartridge drive unit is reduced to an extremely slight value. Thus, chucking failure due to core axis misalignment is prevented.
In accordance with the present invention, there is provided a fourth magnetic tape cartridge comprising:
a cartridge case in which a single reel with magnetic tape wound on an outer periphery of a reel drum is rotatably housed;
an annular reel gear, provided in a bottom surface of the reel drum, which is meshed by an annular drive gear of a rotation-drive member of a cartridge drive unit in an axial direction of the annular drive gear so that the reel is rotated; and
a guide means, provided in two opposed surfaces between the rotation-drive member and the bottom surface of the reel drum, for guiding the reel drum and the rotation-drive member so that when a chucking operation is performed, the center axis of the reel drum is aligned with that of the rotation-drive member.
In the fourth magnetic tape cartridge, the guide means is constructed of a protrusion, formed in one of the two opposed surfaces (the bottom surface of the reel drum and the rotation drive member), which has a conical surface at its upper end portion, and a center bore, formed coaxially with the conical protrusion in the other of the two opposed surfaces, which has an inner peripheral surface into which the conical surface of the protrusion is fitted.
According to the fourth magnetic tape cartridge of the present invention, a guide means is provided in two opposed surfaces between the rotation-drive member and the bottom surface of the reel drum, and guides the reel drum and the rotation-drive member so that when a chucking operation is performed, the center axis of the reel drum is aligned with that of the rotation-drive member. Therefore, even when the magnetic tape cartridge is vertically loaded into a cartridge drive unit and core axis misalignment of the reel drum occurs, the core axis misalignment of the reel is adjusted during chucking, and consequently, chucking failure is prevented.